To research the sand production law and main controlling factors of deep reservoir sandstone under high temperature, high pressure, and high-stress state, the rock mechanics experiments and numerical simulations were carried out using the Keshen block as the object. The experimental cores were taken from the tight sandstone reservoirs in this block, and the elastic modulus, cohesion, and internal friction angle of rocks under high temperature and high pressure were obtained through experiments and their changing rules. By analyzing the variation characteristics of parameters such as 22Mises stress and equivalent plastic strain in the reservoir, combined with the criteria for sand production discrimination, the influence of sand production under different mining conditions was obtained. The factors of sand production sensitivity are analyzed by using the orthogonal design of experiments method, and the main control factors of sand production are obtained. The research results show that the inhomogeneous degree of horizontal stress has the most significant influence on the sand production of the reservoir, followed by the power of rock cement strength and production pressure difference, and the influence of formation temperature change is relatively smaller.